One hundred and thirty symbiotic and non-symbiotic strains of Bradyrhizobium were directly isolated from inoculated soybean and uninoculated legume-free virgin field soils in Thailand using a direct selection medium. About 47% and 58% of the isolates obtained from inoculated and uninoculated fields, respectively, were characterized as being non-symbiotic bradyrhizobia. Partial and nearly full-length sequence analyses of regions encoding 16S rRNA indicated that the non-symbionts were closely related to Bradyrhizobium elkanii (79-99% identity) and Bradyrhizobium japonicum (96-100% identity). Southern hybridization analyses showed that DNA from the non-symbiotic bradyrhizobia failed to hybridize to nif and nod gene probes. rep-PCR DNA fingerprint analyses, done using the BOXA1R primer, indicated the symbionts and non-symbionts could be separated into two distinct clusters. There was no relationship between the geographical origin of isolates and groups made based on serological reaction or their ability to nodulate soybean, cowpea, mungbean, or siratro. These results indicate that a relatively large percentage of non-nodulating bradyrhizobia are present in Thai soils.
|Original language||English (US)|
|Number of pages||20|
|State||Published - Jan 1 2002|
- 16S rDNA
- Soil bacteria
- Soil populations